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Hilsa, one of the most sought-after fish, is gradually going beyond reach for the common man because of its dwindling supplies and escalating costs. The indiscriminate exploitation of Hilsa resources – not sparing even the juveniles – and the destruction of its habitats in rivers and coastal waters are among the main reasons for the depletion of the fish stocks, resulting in smaller catches.

Hilsa (Tenualosa ilisha) is a migratory fish that spends the most part of its lifespan in sea water, and only uses fresh water for breeding. The young ones move back to the sea and grow there. The building of barrages and dams on Hilsa-harbouring rivers is believed to have obstructed the migration routes of the fish — adversely affecting its multiplication. This is borne out by a sharp decline in Hilsa fisheries in the Ganga and Narmada river systems after the construction of Farrakka Barrage and Sardar Sarovar Dam.

Consequently, traditional fishers, who use mostly non-mechanised fishing boats and could earlier gather considerable catches of Hilsa from interior stretches of rivers, now net some quantities only in their estuaries. The landing of Hilsa from coastal waters has reduced significantly owing to overfishing. Besides, unlike most other common commercial fishes, which can be reared in captivity to supplement the supplies from natural sources, Hilsa farming is not possible for want of viable technology. The entire supply, therefore, depends on catches from rivers and marine coasts.

Interestingly, Hilsa fisheries are not confined to the Hooghly-Bhagirathi river system alone, though it remains the most important source of the fish. It also traditionally existed in several other rivers, especially those draining into the Bay of Bengal on the east coast, such as Godavari and Mahanadi, and into the Arabian Sea on the west coast, such as Narmada and Tapti. The Chilka lagoon, too, has been a rich source of Hilsa in the past. Besides, the species is found in the Brahmaputra-Meghna river systems, which constitute a significant part of the commercial capture fisheries in Bangladesh and Myanmar. However, all these rivers have witnessed a sharp decline in Hilsa fisheries in the past couple of decades.

The most worrisome, of course, is the drop in Hilsa catches in the Hooghly estuary — from 44,000 tonnes in 2003-04 to a mere 14,000 tonnes in 2009-10. However, the Hilsa output in this zone saw a remarkable rebound in 2010-11 with the estimated total landing of nearly 60,000 tonnes. Such sudden spurts in Hilsa production happen once in every 10 to 12 years, say fisheries experts of the Barrackpore (Kolkata)-based Central Inland Fisheries Research Institute (CIFRI).

Another unusual phenomenon noticed by the Hilsa watchers, according to the experts, was that this innately migratory fish seemed to have adapted itself to the freshwater environment of the Vallabh Sagar (Ukai) reservoir in Gujarat. This is clear from the steady uptrend in the harvest of table-size Hilsa (weighing over 500 grams) from this dam without any movement of juveniles to marine waters for their growth.

Nevertheless, given the unabated deterioration in Hilsa fisheries in all its traditional habitats, the CIFRI scientists feel that management interventions have become inevitable to reverse this trend. However, such interventions would require clear knowledge of the manner of breeding, feeding, habitat preferences and other characteristics of Hilsa — which is by and large lacking at present. To address this lacuna, the Indian Council of Agricultural Research (ICAR) has proposed to launch a five-year project to study the biology, genetic makeup, reproduction and feeding habits of this unique fish species. It will also look into the stock dynamics of Hilsa in different parts of the country. Seven different institutions, including the ICAR’s fisheries research centres and the Visva-Bharti University, Santiniketan, will participate in this Rs 13.8 crore project, under the overall leadership of the CIFRI.

The outcome of this major research initiative is expected to help evolve workable strategies to sustain Hilsa fisheries in natural water, besides developing technologies for the production of Hilsa seed and artificial feed — the two vital inputs required to facilitate captive rearing of Hilsa. More importantly, it might even pave the way for industrial farming of this highly nutritive and tasty fish species.